It has already been said, but I think it bears repeating...
THERE IS NO WAY ON EARTH I WOULD ATTEND A CHOIR REHEARSAL AT 8:30 A.M. EVERY SATURDAY ON A REGULAR BASIS... I honestly think that is absolutely ridiculous (and possibly a little selfish).
I agree with getting rid of some of those choirs (but I would caution that that's a lot easier said than done in a Baptist church, Jonathan... those folks are traditionalists and it's not easy to get them to STOP doing something that they've done for decades, especially if they feel it works for them).
I also agree that expecting musicians to give up their entire Saturday to rehearse all day is just wrong. Plus, from what I'm gathering, there's a lot of chaos that goes on at your rehearsals... who wants to deal with chaos from 8:30 to 4:00 every single Saturday, all day?
What if the person who sings in one group rehearses at 10 and their next rehearsal is at 1 or 2 or whatever? Do they have to sit there and wait between rehearsals? Leave and come back?
I just wouldn't do that. And for the record, I also wouldn't do 2 rehearsals in one week for the same group (unless there's something special going on).
I do believe that any main or featured choirs/groups (praise team, mass choir, sanctuary choir, etc) should rehearse every week for optimum results (unless they are just THAT GOOD and don't need it). But stuff like men's choir (YUCK!!!) or Seniors Choir or Childrens Choir can manage with once or twice a month.
If Friday is your night for rehearsals, and the goal is to free up time during the week, I would do PT rehearsal from 7-8 and main choir from 8-9:30. And I would use a 3 hour window on Saturdays for all the auxiliary choirs (11-2 or 10-1 would be my opinion, no earlier than 9-12, starting with the seniors since they don't mind getting up early anyway... lol).
